How to edit "skin" instead of edit bones?
This could possibly be because their selection has been limited in the outliner. To make sure this isn't the case, check and see if all of the pointer icons in the outliner are white, and not grey. Click them to change if they are.



This could also be if you are in the wrong mode. Armatures have three modes;


 Object mode is portrayed by an orange cube, it allows you to change which object you can select 
 Edit mode is portrayed by a grey cube with four orange studs on its front (I suspect this is the one you're in) it only allows you to change the shape of the bones in your armature 
 Pose mode is portrayed by a small white man waving his hands around like he's trying to slow down a Taxi, it allows you to wiggle the bones around once they have been shaped right in edit mode. 


You need to switch to object mode in order to select the mesh "skin" of your object.